In commit d2d9f2324, the guard for a valid video mode was removed. This
caused the regression:

kernel crash during kms graphic boot on Intel GM4500 platform
https://bugzilla.redhat.com/show_bug.cgi?id=540218

This patches changes the logic slightly not to rely on a coupled
variable, but to just check whether the video_modes is valid before
dereferencing.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Zhenyu Wang <zhenyu.z.wang@intel.com>
[ickle: Actually reference the correct bug report]
Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
---
drivers/gpu/drm/i915/intel_tv.c | 11 ++++-------
1 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index a0e4bc4..d7465ca 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -1213,20 +1213,17 @@ intel_tv_mode_set(struct drm_encoder *encoder, struct drm_display_mode *mode,
tv_ctl |= TV_TRILEVEL_SYNC;
if (tv_mode->pal_burst)
tv_ctl |= TV_PAL_BURST;
+
scctl1 = 0;
- /* dda1 implies valid video levels */
- if (tv_mode->dda1_inc) {
+ if (tv_mode->dda1_inc)
scctl1 |= TV_SC_DDA1_EN;
- }
-
if (tv_mode->dda2_inc)
scctl1 |= TV_SC_DDA2_EN;
-
if (tv_mode->dda3_inc)
scctl1 |= TV_SC_DDA3_EN;
-
scctl1 |= tv_mode->sc_reset;
- scctl1 |= video_levels->burst << TV_BURST_LEVEL_SHIFT;
+ if (video_levels)
+ scctl1 |= video_levels->burst << TV_BURST_LEVEL_SHIFT;
scctl1 |= tv_mode->dda1_inc << TV_SCDDA1_INC_SHIFT;

scctl2 = tv_mode->dda2_size << TV_SCDDA2_SIZE_SHIFT |
--
1.6.3.3

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